KR20100103850A - Electrode and method for producing electrode - Google Patents

Abstract

An electrode (for example, a lithium ion battery positive electrode) 30 in which an active material layer 35 mainly composed of electrode active materials is held in a metal current collector 32 is provided. On the surface of the current collector 32, a barrier layer 33 containing a conductive material 330 and a water-insoluble polymer material 334 is formed. The conductive material 330 includes at least a first conductive powder 331 having a predetermined average particle diameter and a second conductive powder 332 having a larger average particle diameter than the first conductive powder. The content rate of the 1st conductive powder 331 in the barrier layer 33 is larger than the content rate of the 2nd conductive powder 332.

Description

Electrode and Electrode Manufacturing Method {ELECTRODE AND METHOD FOR PRODUCING ELECTRODE}

This invention relates to the electrode used as a component of a battery (for example, lithium ion battery), and its manufacturing method.

Moreover, this application claims the priority based on Japanese Patent Application No. 2008-013095 for which it applied on January 23, 2008, The whole content of the application is integrated in this specification as a reference.

BACKGROUND ART An electrode having a structure in which a material capable of releasing a species that functions as a charge carrier is held in a current collector is known. As an example of this kind of electrode, the electrode for secondary batteries of the structure which hold | maintained the material (active material) which can reversibly occlude and discharge | release said chemical species in the metal electrical power collector is mentioned. Such an electrode can be suitably used as a positive electrode or a negative electrode for constructing a lithium ion battery which charges and discharges an electrolyte (typically a nonaqueous electrolyte) interposed between the counter electrodes and lithium ion flows. have. As a representative method for holding an active material in a current collector, a method of forming a layer (active material layer) of an active material main body by applying a paste or slurry composition (active material composition) obtained by dispersing the powder of the active material in a solvent (active material composition) to an electrode current collector Can be mentioned. As an active material composition used for this method, the solvent which comprises the said medium (dispersion medium, such as an active material powder) is an aqueous solvent from a viewpoint of reducing an environmental load, reducing a material cost, simplifying an installation, reducing waste, and improving handleability. Phosphorus-based active material composition is preferable.

However, depending on the contents of the active material, problems such as a decrease in battery capacity or a decrease in discharge characteristics due to an increase in initial internal resistance may occur due to the use of an aqueous composition. These may be due to the reaction of the active material and water included in the paste. For example, in the case of using a lithium transition metal oxide such as lithium nickel-based oxide (an oxide containing lithium and one or two or more transition metal elements as a constituent metal element as the positive electrode active material. An exchange reaction of protons and lithium ions occurs on the surface of the positive electrode active material dispersed in the solvent, and as a result, the pH of the aqueous active material composition may be high (ie, alkaline). When such a high pH aqueous active material composition is applied to a positive electrode current collector (for example, made of aluminum), a compound (for example, an oxide or a hydroxide) showing high electric resistance on the surface of the current collector may be easily produced. have. The production of such a high electric resistance compound may be a factor of increasing the initial internal resistance of the battery (and, moreover, a factor that hinders high output).

In this regard, Patent Document 1 forms a layer (conductive layer) containing an organic solvent-soluble polymer (binder) and a conductive material on the surface of a current collector, and prevents direct contact between water and the current collector on this layer. By using it as a barrier layer, the technique of avoiding the idea that the said high electric resistance compound is produced when providing an active material layer by providing an aqueous active material composition from the said layer is described.

Patent Document 1: Japanese Patent Application Publication No. 2006-4739

Here, the barrier layer as described above has water resistance (a performance of preventing direct contact between water and a current collector to prevent the formation of the high-electromagnetic resistive compound) and conductive (in other words, excessive resistance between the active material layer and the current collector layer). Not rising). However, these two characteristics are usually in a betrayal relationship. For example, increasing the content ratio of the conductive material in the barrier layer is advantageous for improving the conductivity of the electrode having the barrier layer. However, simply increasing the ratio results in a relatively low content ratio of the binder, so that the barrier layer is relatively low. The water resistance of the tends to be lowered. On the contrary, when the content ratio of the binder is increased to improve the water resistance of the barrier layer, the content ratio of the conductive material is relatively small, and the conductivity tends to be lowered.

Therefore, this invention solves the problem at the time of manufacturing an electrode (for example, a lithium ion battery positive electrode) using an aqueous active material composition at a higher level, and exhibits stable high performance even if it manufactures using an aqueous active material composition. It is an object to provide an electrode. Another object of the present invention is to provide a method for producing a high performance electrode using an aqueous active material composition. Moreover, an object of this invention is to provide the lithium ion battery other battery constructed using such an electrode, and the vehicle provided with the said battery.

According to the present invention, there is provided an electrode (eg, a lithium ion battery positive electrode) in which an active material layer containing an electrode active material as a main component is held in a metal current collector. On the surface of the current collector, a barrier layer containing a conductive material and a water-insoluble polymer material is formed. The said electrically-conductive material contains the 1st electroconductive powder of a predetermined average particle diameter (it refers to the average particle diameter of the particle | grains which comprise this powder. It is the same below.), And the 2nd electroconductive powder whose average particle diameter is larger than the said 1st electroconductive powder. It is preferable to make the content rate of the said 1st conductive powder in the said barrier layer larger than the content rate of the said 2nd conductive powder.

According to the electrode of such a structure, by mixing (combining) a relatively small particle size of the first conductive powder and a relatively large particle size of the second conductive powder, compared with the case of simply using only the first conductive powder as the conductive material, the conductive The fall of the water resistance accompanying the increase of content of ash can be suppressed. That is, the conductivity of a barrier layer can be improved, suppressing the fall of water resistance. Therefore, the barrier is maintained while maintaining high water resistance in the barrier layer (for example, water resistance capable of sufficiently preventing generation of the high-electromagnetic resistant compound even in the case of forming an active material layer using an aqueous active material composition). A high performance electrode can be provided in which the conductivity of the layer (preferably, the conductivity between the active material layer and the current collector) is improved. The battery provided with such an electrode can be a higher performance (for example, higher output).

In addition, in this specification, a "battery" is a term which refers to the general electrical storage device which can extract electrical energy, and it is a secondary battery (lithium ion battery, a metal lithium secondary battery, nickel hydrogen battery, nickel cadmium battery, etc.). A so-called storage battery and an electrical storage element such as an electric double layer capacitor) and a primary battery.

It is preferable that the average particle diameter of the said 2nd conductive powder is about 2 times or more (typically about 2 to 500 times) of the average particle diameter of the said 1st conductive powder. Thus, by using the 2nd electroconductive powder whose particle diameter is remarkably large compared with a 1st electroconductive powder, in the composition (composition for barrier layer formation) which melt | dissolved or disperse | distributed the constituent component of the said barrier layer to a suitable solvent, In comparison, the viscosity of the composition can be made relatively low. Therefore, the handleability at the time of forming a barrier layer on the surface of an electrical power collector using the said composition (coating property, etc. when giving the said composition to an electrical power collector (for example, gravure coating)) is practically good enough range. In, the solid content concentration of the composition can be made higher. This is preferable from the viewpoint of reduction of time and energy required for drying the composition for barrier layer formation, reduction of the amount of solvent used, and the like.

In a preferable embodiment of the electrode disclosed herein, the average particle diameter of the second conductive powder is larger than the thickness of the barrier layer. In other words, a plurality of (typically many) convex portions are formed on the surface of the barrier layer by protruding the particles constituting the second conductive powder. Thus, by making the surface into the uneven | corrugated shape, the surface area (contact area with an active material layer) of a barrier layer increases. According to the electrode of such a structure, the conductive path between a barrier layer and an active material layer is formed better, and the electron transfer between these layers can be performed more efficiently (in other words, the interface resistance of a barrier layer and an active material layer can be reduced. ). Thus, a higher performance electrode can be provided.

According to the present invention, there is also provided a method of producing an electrode (for example, a lithium ion battery positive electrode) having a structure in which an active material layer containing an electrode active material as a main component is held in a metal current collector. The method includes preparing a composition for barrier layer formation comprising a conductive material, a water-insoluble polymer material, and a solvent in which the polymer material is dissolved. Here, the said barrier layer forming composition uses the 1st conductive powder which is a predetermined average particle diameter, and the 2nd conductive powder whose average particle diameter is larger than the said 1st conductive powder as said electrically conductive material, and the said 1st conductive powder of It is prepared so that content rate may become larger than content rate of the said 2nd electroconductive powder. The electrode manufacturing method disclosed here further includes providing the barrier layer-forming composition to the current collector to form a barrier layer on the surface of the current collector. The method also includes forming an active material layer by applying an aqueous active material composition to a current collector on which the barrier layer is formed.

According to this manufacturing method, since the barrier layer is formed on the surface of the current collector prior to the provision of the active material composition, the barrier layer can prevent contact between the aqueous active material composition and the surface of the current collector. Therefore, regardless of the use of the water-based active material composition, the generation of the high electric resistance compound can be appropriately prevented. In addition, as described above, the barrier layer formed by using the barrier layer-forming composition is suppressed from deteriorating the barrier property accompanying the increase in the content of the conductive powder. Therefore, according to the above production method, a high-performance electrode (preferably, an electrode capable of constructing a higher-performance battery) is produced in which the increase in resistance between the active material layer and the current collector is suppressed while securing high water resistance in the barrier layer. can do.

In a preferable embodiment of the electrode manufacturing method disclosed herein, the first conductive powder is added to the mixture after the second conductive powder and the non-aqueous polymer material are mixed with the solvent for preparing the composition for forming the barrier layer. By mixing. According to the said preparation form, the 1st conductive powder with a relatively small particle diameter can be disperse | distributed more uniformly in the composition for barrier layer forming. According to such a composition, the 1st conductive powder is disperse | distributed more uniformly, Therefore, the barrier layer with more electroconductivity can be formed.

In another preferable aspect of the electrode manufacturing method disclosed here, the solvent which comprises the said composition for barrier layer formation is an organic solvent. By using the composition for barrier layer formation (i.e., solvent-based composition) having such a composition, a barrier layer having better water resistance (e.g., which can prevent contact between water and the surface of the current collector for a longer time) can be formed. Can be.

According to the present invention, there is also provided a battery (eg, a secondary battery, preferably a non-aqueous secondary battery) constructed using any of the electrodes disclosed herein. The battery using such an electrode can be made more efficient since the generation of the high electric resistance compound is prevented on the surface of the current collector constituting the electrode and the conductivity between the active material layer and the current collector is improved. The lithium ion battery constructed by using any one of the electrodes disclosed herein as the positive electrode is a typical example of the battery provided by the present invention.

According to the invention, there is also a vehicle provided with any one lithium ion battery disclosed herein (which may be a lithium ion battery comprising, for example, an electrode produced by any of the methods disclosed herein as a positive electrode). This is provided. The lithium ion battery may realize high performance (for example, stably exerting high output) suitable as a lithium ion battery mounted in a vehicle. Therefore, it can be suitably used as a power source for a motor (motor) mounted on a vehicle such as an automobile.

BRIEF DESCRIPTION OF THE DRAWINGS It is typical sectional drawing for demonstrating the function of the electrode which concerns on one Embodiment.
2 is a flowchart illustrating a schematic manufacturing method of an electrode according to one embodiment.
3 is a schematic perspective view showing a battery according to an embodiment.
4 is a schematic plan view showing a stationary electrode and a separator constituting a battery according to an embodiment.
5 is a cross-sectional view taken along the line VV of FIG. 3.
6 is a schematic side view illustrating a vehicle (car) provided with a lithium ion battery according to one embodiment.
7 is a schematic cross-sectional view for explaining the function of an electrode according to another embodiment.
8 is a graph showing the relationship between the content of the second conductive powder, the film resistance, and the water resistance.
9 is a graph showing the relationship between the addition rate of the first conductive powder and the film resistance.
10 is a schematic cross-sectional view for explaining the function of the electrode not containing the second conductive powder.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of this invention is described. In addition, matters other than what is specifically mentioned in this specification, matters necessary for implementation of this invention can be grasped | ascertained as the design matter of those skilled in the art based on the prior art in the said field | area. This invention can be implemented based on the content disclosed by this specification and technical common sense in the said field | area.

The technique disclosed herein is, for example, an electrode having a structure in which an active material layer is held in a current collector, and when the aqueous active material composition is used for formation of the active material layer, the liquidity of the composition tends to be alkaline. The present invention can be suitably applied to various electrodes provided with the active material capable of contacting with water and shifting the liquidity toward the alkali side, and the production thereof. Representative examples of such active materials include lithium transition metal oxides such as lithium nickel-based oxides.

When the material of the current collector constituting the electrode is a material capable of producing a compound exhibiting high electric resistance on the surface by contacting with an alkaline aqueous composition, the effect by applying the technique disclosed herein will be particularly well exhibited. Can be. As a representative example of such a material, aluminum materials, such as aluminum (Al) and the alloy (aluminum alloy) which has aluminum as a main component, are mentioned. As another example, amphoteric metals, such as zinc (Zn) and tin (Sn), and the alloy which has any one of these metals as a main component is mentioned.

The shape of the current collector to be used may vary depending on the shape of a battery (typically a secondary battery) constructed using the obtained electrode, and the like, and there is no particular limitation, and there are no rods, plates, sheets, foils, or meshes. It may be in various forms such as. The technique disclosed here can be suitably applied to manufacture of an electrode using a sheet-like or foil-shaped current collector, for example. As a preferable embodiment of the battery constructed using the electrode manufactured by such a method, a battery having an electrode body (wound electrode body) formed by winding a sheet-shaped positive electrode and a negative electrode with a sheet-shaped separator is typically provided. Can be mentioned. The external shape of the battery is not particularly limited, and may be, for example, an external shape such as a rectangular parallelepiped shape, a flat shape, and a cylindrical shape.

As a typical example of the electrode to which the technique disclosed herein is preferably applied, an active material layer containing lithium transition metal oxide as an active material and having the active material as a main component is held in a current collector made of aluminum material for a lithium ion battery. A positive electrode is mentioned. Hereinafter, the present invention will be described in more detail with reference to the case where the present invention is mainly applied to a positive electrode for a lithium ion battery and its manufacture and a lithium ion battery constructed by using the electrode, but the application of the present invention is described in the application of such an electrode or a battery. It is not intended to be limited to.

As a lithium transition metal oxide (typically, particulate) which is an active material (main component of an active material layer) of a positive electrode for a lithium ion battery, an oxide having a layer structure or an oxide having a spinel structure that can function as a positive electrode active material of this kind of lithium ion battery. It can be selected appropriately. For example, use of one or two or more lithium transition metal oxides selected from lithium nickel oxides, lithium cobalt oxides, and lithium manganese oxides is preferable. A particularly preferable application object of the technique disclosed herein is a positive electrode made of lithium nickel oxide as a positive electrode active material (typically, the positive electrode active material substantially consists of lithium nickel oxide). In comparison with lithium cobalt oxide and lithium manganese oxide, lithium nickel oxide has a tendency to be more easily eluted when Li is dispersed in an aqueous solvent (thus, the effect of shifting the liquidity of the aqueous active material composition toward the alkali side) tends to be higher. . Therefore, in manufacture of the electrode which uses lithium nickel type oxide as a positive electrode active material, the effect by applying the method disclosed here can be exhibited especially well.

Herein, the term "lithium nickel-based oxide" means one or two or more metal elements other than Li and Ni (ie, transition metal elements other than Li and Ni and / or oxides other than Li and Ni as constituent metal elements). It is also meant to include a composite oxide containing a typical metal element in a proportion less than Ni (atomic number conversion. In the case of containing two or more kinds of metal elements other than Li and Ni, the proportion is less than Ni in any of them). Such metal elements are selected from the group consisting of, for example, Co, Al, Mn, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, copper, Zn, Ga, In, Sn, La and Ce It may be one kind or two or more kinds of elements. Similarly, "lithium cobalt oxide" means a complex oxide containing one or more metal elements other than Li and Co in a smaller proportion than Co, and "lithium manganese oxide" means In addition to Li and Mn, it is meant to include a composite oxide containing one or two or more metal elements in a smaller proportion than Mn.

As such a lithium transition metal oxide (typically, particulate form), for example, a lithium transition metal oxide powder (hereinafter sometimes referred to as an active material powder) prepared and provided by a conventionally known method can be used as it is. For example, in the technique disclosed herein, a lithium transition metal oxide powder composed substantially of secondary particles having an average particle diameter in the range of about 1 μm to 25 μm (typically about 2 μm to 15 μm) It can be employ | adopted suitably as a positive electrode active material of.

The positive electrode active material composition used in the method disclosed herein may be an aqueous composition in which such an active material is dispersed in an aqueous solvent. In addition, the positive electrode active material disclosed here may be formed using such an aqueous composition. Here, "aqueous solvent" is a concept which points out the water or the mixed solvent which mainly uses water. As a solvent other than water which comprises the said mixed solvent, 1 type (s) or 2 or more types of the organic solvent (lower alcohol, lower ketone etc.) which can be mixed uniformly with water can be selected suitably, and can be used. For example, use of the aqueous solvent in which about 80 mass% or more (more preferably about 90 mass% or more, still more preferably about 95 mass% or more) of the said aqueous solvent is water is preferable. As an especially preferable example, the aqueous solvent which consists of water substantially is mentioned. Although it does not specifically limit, solid content concentration (non-volatile content, ie, the ratio of an active material layer formation component) of a positive electrode active material composition may be about 40-60 mass%, for example.

The said positive electrode active material composition typically contains the electrically conductive material which raises the electroconductivity of the positive electrode active material layer formed from the said composition other than a positive electrode active material and an aqueous solvent. As such a conductive material, for example, carbon materials such as carbon powder and carbon fiber are preferably used. Or you may use electroconductive metal powder, such as nickel powder. Only 1 type may be used among these and 2 or more types may be used together. As carbon powder, carbon powder, such as various carbon black (for example, acetylene black, furnace black, Ketjen black), graphite powder, can be used. Of these, acetylene black can be preferably employed. For example, a particulate conductive material (eg, acetylene black) in which the average particle diameter of the constituent particles (typically primary particles) is in the range of about 10 nm to 200 nm (eg, about 20 nm to 100 nm). Granular carbon materials).

In addition, the said positive electrode active material composition can contain the 1 type (s) or 2 or more types of material which can be mix | blended with a positive electrode active material composition (typically an aqueous composition) in manufacture of a general lithium ion battery positive electrode as needed. As an example of such a material, various polymer materials which can function as a binder (binder) of a positive electrode active material are mentioned. As such a polymer material, in preparing an aqueous active material composition, a polymer material conventionally used as a binder can be appropriately selected and used. Preference is given to the use of polymeric materials which are substantially insoluble in organic solvents and which dissolve or disperse in water. For example, as the polymer material dissolved in water (water-soluble), carboxymethyl cellulose (CMC), methyl cellulose (MC), cellulose acetate cellulose (CAP), hydroxypropyl methyl cellulose (HPMC), hydroxypropyl methyl cellulose Cellulose derivatives such as phthalate (HPMCP); Polyvinyl alcohol (PVA); Water-soluble polymers, such as these, are mentioned. Especially, CMC can be employ | adopted preferably. As the polymer material dispersed in water (water dispersible), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene Fluorine resins such as copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), vinyl acetate copolymer, styrene butadiene block copolymer (SBR), acrylic acid modified SBR resin (SBR-based latex), gum arabic Rubbers are illustrated. Especially, fluorine-type resins, such as PTFE, can be used preferably. Only 1 type may be used among these polymer materials, and 2 or more types may be used together.

The proportion of the positive electrode active material (typically approximately equal to the proportion of the positive electrode active material in solid content of the positive electrode active material composition) in the entire positive electrode active material layer is preferably about 50 mass% or more (typically 50 to 95 mass%). And it is more preferable that it is about 75-90 mass%. In the positive electrode active material layer of the composition containing a electrically conductive material, the ratio of the electrically conductive material to the said active material layer can be made into about 3-25 mass%, for example, It is preferable to set it as about 3-15 mass%. In this case, it is suitable that the ratio of the positive electrode active material to the active material layer is about 80 to 95 mass% (for example, 85 to 95 mass%).

In addition, in the composition containing a positive electrode active material layer forming component (for example, a polymer material) other than a positive electrode active material and a electrically conductive material, about 7 mass of the total content ratio (the ratio which occupies for the whole positive electrode active material layer forming component) of these arbitrary components is included. It is preferable to set it as% or less, and it is more preferable to set it as about 5 mass% or less (for example, about 1-5 mass%). The sum total content rate of the said arbitrary component may be about 3 mass% or less (for example, about 1-3 mass%).

In the method disclosed here, a barrier layer is previously formed on the surface of an electrical power collector, and the said positive electrode active material composition is provided from the said barrier layer, and an active material layer is formed. Hereinafter, the structure and formation method of the said barrier layer are explained in full detail.

The barrier layer contains a water-insoluble polymer material (typically a polymer material that is substantially insoluble in neutral to alkaline water) and a conductive material. As this water-insoluble polymer material, one or two or more kinds of materials capable of forming a water-resistant coating on the surface of the current collector can be appropriately selected and used. It is preferable to employ an electrolyte (typically a liquid electrolyte, i.e., an electrolyte) of a battery (typically a lithium ion battery) constructed using the electrode and a material resistant to battery reaction. As such a water-insoluble polymer material, for example, polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene oxide-propylene oxide copolymer (PEO-PPO) ) Can be used. Among them, the use of PVDF is preferred.

The electrically-conductive material used for the structure of the barrier layer contains at least 1st electrically conductive powder and 2nd electrically conductive powder whose average particle diameter is larger than the said 1st electrically conductive powder. Although the size of the particles constituting each conductive powder may be substantially the same (that is, monodispersed), usually, the first and second conductive powders having a predetermined particle size distribution are preferably used. Thus, the particle size distribution of the whole electrically conductive material containing two types of powder which respectively have a particle size distribution and differs from each other in average particle diameter (here, 1st, 2nd conductive powder) is typically bimodal.

As each of these 1st, 2nd electroconductive powder, a carbon material, electroconductive metal powder, etc. can be used similarly to the electrically conductive material illustrated as a structural component of an active material composition (active material layer). Especially, use of granular carbon materials, such as acetylene black, is preferable. The first conductive powder and the second conductive powder may be homogeneous materials (for example, all acetylene black), or different materials (for example, a combination of acetylene black and Ketjen black, and a combination of acetylene black and carbon fiber). good. Combinations of homogeneous materials having different average particle diameters (particularly combinations of acetylene blacks) can be preferably employed.

Although not particularly limited, the average particle diameter of the first conductive powder is preferably in the range of about 10 nm to 200 nm (more preferably about 20 nm to 100 nm, for example, about 20 nm to 50 nm). On the other hand, as a 2nd electroconductive powder, what has an average particle diameter larger than a 1st electroconductive powder is used. For example, the ratio (ie, D2 / D1) of the average particle diameter D2 of the second conductive powder to the average particle diameter D1 of the first conductive powder is preferably about 1.2 or more, more preferably about 1.5 or more, More preferably about 2 or more. Although the upper limit of D2 / D1 is not specifically limited, Usually, it is preferable that it is 200 or less. For example, a 2nd conductive powder whose average particle diameter is 30 nm-10 micrometers (more preferably 50 nm-5 micrometers), and satisfy | fills said D2 / D1 can be used preferably.

The more preferable average particle diameter of a 1st conductive powder and a 2nd conductive powder may also differ with thickness of a barrier layer. For example, as the first conductive powder, the average particle diameter D1 is about 1/20 or less (typically about 1/200 to 1/20, preferably about 1/100 to) of the thickness T _B of the barrier layer. 1/40) can be used preferably. On the other hand, as the second conductive powder, the average particle diameter D2 is larger than D1 (that is, D1 <D2) and D2 is about 1/60 or more (typically about 1/40) of the thickness T _B of the barrier layer. Or more). D2 is also preferably can be a second conductive powder is greater than T _B. Although the upper limit of D2 is not specifically limited, Usually, it is preferable to set it as 4 times or less (preferably 3 times or less) of the thickness T _B of a barrier layer. Further, the thickness of which in the case of using the second conductive powder of D2> T _B as described above, the term "thickness of the barrier layer" is calculated by dividing the mass of the barrier layer formed on the unit area by the density of the barrier layer ( Average thickness).

The mass ratio of the conductive material (including the first and second conductive powders) / polymer material in the barrier layer (typically approximately equal to the mass ratio of the conductive material / polymer material included in the barrier layer-forming composition) is For example, about 60/40 or less (typically about 10/90 to 60/40), and about 50/50 or less (typically about 20/80 to 50/50, for example about 30 / 70 to 40/60). When the said mass ratio is too small than the said range, it will become difficult to ensure sufficient conductive path (conductive path) in a barrier layer, and the electroconductivity of an electrode may become the tendency for a fall. On the other hand, when the mass ratio of the conductive material / polymer material is too large than the above range, the water resistance of the barrier layer may tend to be lowered.

It is preferable that the barrier layer disclosed here contains a 1st conductive powder in a ratio (mass ratio) more than 2nd conductive powder. For example, the barrier layer which contains a 2nd conductive powder in the ratio of about 1 mass part or more and less than 100 mass parts (more preferably about 10-50 mass parts) with respect to 100 mass parts of 1st conductive powder is preferable. When the use ratio of the 2nd conductive powder with respect to 1st conductive powder is too small than the said ratio, the effect by using both powders may be hard to fully be exhibited. On the other hand, when there is too much use ratio of the 2nd conductive powder with respect to a 1st conductive powder, water resistance may fall easily.

Such barrier layers are typically prepared by adding and mixing the conductive material (including at least the first and second conductive powders) and the non-aqueous polymer material in a suitable (typically, soluble in the polymer material) solvent. It can be formed by applying the barrier layer forming composition to the surface of the current collector and drying it. The solvent which comprises the said composition can be suitably selected considering the combination with the water-insoluble polymer material to be used. The organic solvent (non-aqueous solvent) used for preparation of the conventional solvent type active material layer formation paste can be used suitably. N-methyl-2-pyrrolidone (NMP), methyl ethyl ketone, toluene, etc. are illustrated as such an organic solvent. Among these, for example, NMP can be preferably employed. Although not particularly limited, the solid content concentration (non-volatile content, that is, the ratio of the barrier layer forming component, hereinafter referred to as "NV") of the composition for barrier layer forming is, for example, about 1 to 30% by mass (preferably About 5-20% by mass). When NV is too high, the handleability of the composition for barrier layer formation (for example, coating property when giving the said composition to an electrical power collector (especially thin current collector) etc.) may fall easily. In addition, when NV is too low, since the amount of the organic solvent to be used increases, there exists a tendency for it to become high cost.

Although not particularly limited, in preparing the composition for forming a barrier layer, first, the second conductive powder and the polymer material are mixed with a solvent (mixed until the polymer material and the second conductive powder are uniformly dissolved and dispersed). It is preferable to employ | adopt the form which mix | pours and disperse | distributes a 1st electrically conductive powder to this mixture, preferably. This form is suitable for preparing the composition for barrier layer formation in which the 1st electrically conductive powder with a relatively small average particle diameter (hence, it tends to be difficult to disperse | distribute uniformly) is uniformly dispersed. The first conductive powder may be added at a time, may be divided into several times, or may be performed gradually (continuously). For example, the total amount of the first conductive powder to be used is divided (typically equally) into 2 to 50 times (more preferably, 3 to 20 times, for example, 5 to 10 times), and they are separated by a predetermined interval ( For example, it is preferable to add at intervals of about 3 to 10 minutes. In addition, either a polymer material and a 2nd conductive powder may mix with a solvent first, and both may mix with a solvent substantially simultaneously.

The operation of applying the barrier layer-forming composition to the current collector surface can be appropriately performed using a conventionally known appropriate coating apparatus (slit coater, die coater, comma coater, gravure coater, etc.). After application | coating, a barrier layer is formed by drying a coating (at this time, you may use suitable drying promotion means (heater etc.) as needed). The coating amount of the barrier layer-forming composition is not particularly limited, but if the coating amount is too small, the water resistance of the barrier layer formed tends to be low, and if the coating amount is too large, the conductivity of the barrier layer (advancing, electrode) is lowered. It may become. From these balances of water resistance and conductivity, it is usually appropriate to set the coating amount to about 0.1 to 10 g / m 2 (solid content basis) per side of the current collector, for example, to about 1 to 5 g / m 2 (solid content basis). desirable.

An operation (typically including a coating operation of the composition and a drying operation of the coating material) of imparting the active material composition on the barrier layer to form the active material layer provides the barrier layer-forming composition on the surface of the current collector and the barrier layer. It can be performed in the same manner as the operation for forming the. The application amount of the active material composition is not particularly limited and may be appropriately different depending on the shape and the use of the positive electrode and the battery. For example, the active material layer is formed relatively thick so that the ratio (barrier layer: active material layer) of the thickness of the barrier layer and the thickness of the active material layer is approximately 1: 5 to 1: 100 (typically a thickness ratio after pressing). It is preferable.

Thus, the positive electrode sheet of the target thickness can be obtained by pressing the laminated body (positive electrode) obtained in this way to the thickness direction as desired. As a method of performing the said press, the conventionally well-known roll press method, the flat plate press method, etc. can be employ | adopted suitably.

In addition, when using a carbon material as a electrically conductive material used for manufacture of an electrode, it is preferable to select a thing with few volatile matters as said carbon material (for example, acetylene black). The low volatile content of the carbon material may be related to the low functional group on the surface of the carbon material. A carbon material having a low surface functional group generates gas by contact of the carbon material with an electrolyte (typically an electrolyte solution) when, for example, a battery is constructed using the carbon material and conditioned by a conventional method. It is preferable because it tends to have a small amount of action (as a result, a small amount of gas generated by conditioning). For example, the use of a carbon material having a volatile matter measured in accordance with JIS K6221 of about 1% or less (typically about 0.1 to 1%) is preferred.

Preferable aspects of manufacturing an electrode (for example, a lithium ion battery positive electrode) by the manufacturing method disclosed herein are shown in the electrode cross-sectional view (only one side of the current collector is shown) shown in FIG. 1 and in FIG. 2. It demonstrates with the flowchart shown, as follows. That is, first, an electrical power collector (for example, aluminum foil) 32 is prepared (step S100). On the other hand, the composition for barrier layer formation containing the 1st conductive powder 331, the 2nd conductive powder 332, and the water-insoluble polymer material 334 is prepared (step S110). The barrier layer forming composition prepared in step S110 is applied to one or both surfaces of the current collector 32, and the imparted material is dried to form the barrier layer 33 (step S120). Next, from the barrier layer 33 formed in step S120, an aqueous active material composition containing an active material (for example, lithium nickel-based oxide powder) 351, a conductive material 352, and a polymer material 354. And the above-mentioned substance is dried to form the active material layer 35 (step S130). Thereafter, the whole is pressed or cut to a desired size as necessary to obtain an electrode 30 having a desired thickness and size.

Here, the time from the provision of the active material composition to the drying of the provision can be set in consideration of the degree of water resistance of the barrier layer constituting the electrode. For example, what is necessary is just to dry the said active material composition for a short time rather than the water resistance period (it can be grasped by the water resistance test described in the Example mentioned later) of the said barrier layer. This makes it possible to stably produce an electrode of high performance (e.g., the production of the high-electromagnetic resistance compound is better prevented, i.e., suitable for constructing a high-output battery). In view of production efficiency of the electrode, degree of freedom in line design, and the like, a practically preferable embodiment of the electrode disclosed herein realizes water resistance (water resistance period) of about 2 minutes or more in the water resistance test described in Examples described later. Barrier layer. More preferably, the barrier layer has a water resistance period of about 3 minutes or more (more preferably, 4 minutes or more). In the film resistance measurement described in Examples described later, a barrier layer having a film resistance of 7 mΩ / cm 2 or less (more preferably 6 mΩ / cm 2 or less) is preferable.

The electrode thus formed is, for example, a barrier layer 33 including a conductive material 330 and a water-insoluble polymer material 334 on the surface of the current collector 32 as shown in the schematic cross-sectional view shown in FIG. 1. And an active material layer 35 including an active material 351, a conductive material 352, and a polymer material 354 on the barrier layer 33. The conductive material 330 included in the barrier layer 33 is made of a relatively small first conductive powder 331 and a relatively large second conductive powder 332.

Here, as shown in the schematic cross-sectional view shown in FIG. 10, as the conductive material 330 constituting the barrier layer 33, for example, a conductive material having the same particle size as the first conductive powder 331 shown in FIG. 1. In the barrier layer 33 including only the ash, when attempting to ensure sufficient water resistance in practical use, the conductive material 330 is blocked by the polymer material 334, and the active material layer 35 and the current collector 32 are separated. Since the conductive paths are reduced or the particle diameter of the conductive material 330 is small, the conductive paths tend to be thin.

According to the electrode of the structure shown in FIG. 1, since the 2nd conductive powder 332 is added to the structure shown in FIG. 10, the 2nd conductive powder 332 is interposed between the 1st conductive powder 331. A thick conductive path can be formed, whereby electron transfer between the active material layer 35 and the current collector 32 can be performed more efficiently. As a result, the conductivity of the barrier layer 33 can be improved.

In addition, the barrier layer in the technique disclosed here may be a composition substantially comprising only the first conductive powder and the second conductive powder as the conductive material, or the first and the first layer within a range that does not significantly impair the effects of the present invention. In addition to the second conductive powder, the third and subsequent conductive powders may be included. In a preferable embodiment, the conductive material included in the barrier layer is substantially composed of only the first conductive powder and the second conductive powder.

The electrode provided by this invention is used suitably as an electrode (for example, positive electrode) for building the battery of various forms. For example, a separator (electrolyte) spaced apart from a positive electrode formed using the electrode, a negative electrode having a negative electrode active material layer held on the negative electrode current collector, an electrolyte disposed between the positive electrode, and typically a positive electrode current collector In the case of this solid, it may not be necessary) and is suitable as a component of the lithium ion battery. The structure of the outer container constituting such a battery (for example, a metal housing or laminate film structure) or the size, or the structure of an electrode body having a positive electrode current collector as a main component (for example, a wound structure or a laminated structure). There is no restriction | limiting in particular about etc.

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of the positive electrode provided by this invention and the lithium ion battery provided with the said positive electrode is demonstrated, referring the schematic diagram shown to FIG. 1, FIG.

As shown in the drawing, the lithium ion battery 10 according to the present embodiment includes a housing (outer container) 12 made of metal (suitable for resin or laminated film), and in the housing 12 Wound electrode body 20 constructed by laminating a long sheet-shaped positive electrode sheet 30, separator 50A, negative electrode sheet 40, and separator 50B in this order and subsequently winding in a flat shape. Is accepted.

The positive electrode 30 is manufactured by applying any of the methods disclosed herein, and has a long sheet-like positive electrode current collector 32 and a barrier layer 33 formed on one or both surfaces of the current collector (FIG. 1) and the positive electrode active material layer 35 formed on the barrier layer. It is preferable that these layers 33 and 35 are typically formed in substantially the same range of the positive electrode electrical power collector 32 (so that they may overlap substantially completely). Alternatively, for example, the barrier layer 33 may be formed more widely than the active material layer 35. It is preferable that the barrier layer 33 is formed so as to cover the entire range in which the active material layer 35 is formed.

On the other hand, the negative electrode 40 includes a long sheet-like negative electrode current collector 42 and a negative electrode active material layer 45 formed on the surface thereof. As the negative electrode current collector 42, a sheet material (typically metal foil such as copper foil) made of metal such as copper can be preferably used. As a negative electrode active material, the carbon material (for example, natural graphite) which contains a graphite structure (layered structure) in at least one part can be used suitably. The negative electrode active material is mixed with a binder (the same as the polymer material in the active material layer on the positive electrode side, etc. can be used) and a conductive material (the same as the active material layer on the positive electrode side, etc. can be used) as needed. To prepare a negative electrode active material composition (preferably an aqueous composition) on one or both surfaces of the negative electrode current collector 42. Subsequently, the negative electrode active material layer 45 can be formed on a desired portion of the current collector 42 by drying the coating material (FIG. 4). Although it does not specifically limit, the usage-amount of a binder with respect to 100 mass parts of negative electrode active materials can be, for example in the range of 0.5-10 mass parts.

As the separators 50A and 50B to be superposed on the positive electrode sheet, for example, a porous film made of polyolefin resin such as polyethylene or polypropylene can be suitably used.

As shown in FIG. 4, one end portion in the longitudinal direction of the positive electrode sheet 30 and the negative electrode sheet 40 is not coated with the active material composition, thus forming a portion where the active material layers 35 and 45 are not formed. do. When superimposing electrode sheets 30 and 40 overlap with two separators 50A and 50B, both active material layers 35 and 45 overlap, and the active material layer unformed portion of the positive electrode sheet and the active material layer of the negative electrode sheet are not. The stationary pole sheets 30 and 40 are slightly shifted and overlapped so that the formation portions are disposed separately at one end portion and the other end portion in the longitudinal direction. In this state, a total of four sheets 30, 40, 50A, and 50B are wound, and the wound electrode body 20 having a flat shape is obtained by pressing and crushing the wound body obtained subsequently from the lateral direction.

Subsequently, the wound electrode body 20 thus obtained is accommodated in the housing 12 (FIG. 5), and an external connection portion is partially disposed outside the housing 12 in which the active material layer unformed portions of the positive electrode and the negative electrode are disposed. It electrically connects with each of the positive electrode terminal 14 and the negative electrode terminal 16 for external connection. Then, a suitable nonaqueous electrolyte solution (for example, a suitable amount of a lithium salt such as LiPF ₆ dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC)) is disposed in the housing 12. And the opening of the housing 12 is sealed by welding of the housing and the lid member 13 corresponding thereto, and the construction (assembly) of the lithium ion battery 10 is completed. In addition, the sealing process of the housing | casing 12 and the arrangement | positioning (pouring) process of electrolyte solution should just be the same as the method performed by manufacture of the conventional lithium ion battery, and do not characterize this invention.

Hereinafter, although some Examples concerning this invention are described, it is not what intended limiting this invention to what shows this specific example.

<Example 1>

Using a sheet of aluminum foil as a current collector, a sheet-like electrode having a lithium nickel-based oxide (lithium nickelate) having a composition represented by LiNiO ₂ was produced.

In other words, acetylene black (AB) (conductive material) and PVDF (polymer material) having an average particle diameter of 35 nm were used in such a manner that the mass ratio of these materials was 30:70, and NV was about 9 mass%. It mixed and prepared the composition for barrier layer formation of a solvent system.

The barrier layer was formed on both surfaces of the said electrical power collector by apply | coating this barrier layer forming composition to both surfaces of the elongate aluminum foil (current collector) of thickness 15micrometer, and drying it. Here, a gravure coater was used to apply the composition, and the coating weight thereof was adjusted to be about 2 g / m 2 (solid content basis) per side of the current collector. In addition, this coating weight [g / m <2>] is substantially equivalent to the thickness (namely, dry film thickness) [micrometer] of the barrier layer formed after drying. That is, according to the application amount, a barrier layer having a thickness of about 2 μm is formed.

<Example 2>

A composition for forming a barrier layer was prepared in the same manner as in Example 1 except that the mass ratio of AB and PVDF having an average particle diameter of 35 nm was 35:65. Using this composition, a barrier layer having a thickness of about 2 μm was formed on both surfaces of the current collector in the same manner as in Example 1.

<Example 3>

In this example, AB (first conductive powder) having an average particle diameter of 35 nm and AB (second conductive powder) having an average particle diameter of 55 nm were used as the conductive material. The said 1st, 2nd electroconductive powder and PVDF were mixed with NMP so that the mass ratio of these materials might be 30: 5: 65, and NV might be about 9 mass%, and the composition for barrier layer formation was prepared. Using this composition, a barrier layer having a thickness of about 2 μm was formed on both surfaces of the current collector in the same manner as in Example 1.

The performance of the barrier layer forming current collector produced by Examples 1 to 3 was evaluated by the following water resistance test and film resistance measurement. The result is shown in Table 1 with the schematic structure of the barrier layer which concerns on each example.

[Water resistance test]

0.1 mol / L of sodium hydroxide (NaOH) aqueous solution was added dropwise to the surface of the barrier layer-forming current collector (that is, the surface of the barrier layer) according to each example, and left for 300 seconds (ie, 5 minutes), and the barrier layer was peeled off. The time until (a domestic period) was observed.

[Membrane resistance measurement]

The barrier layer forming electrical power collector which concerns on each case was sandwiched between two copper plates, the pressure of 2500N was applied, and the sheet resistance [ohm * cm <2>] was measured by the 4-terminal 4 probe method based on JISK7194.

As shown in Table 1, in Examples 1 and 2 using only AB having an average particle diameter of 35 nm as the conductive material, when the content ratio of the conductive material was increased from 30% by mass to 35% by mass, the conductivity of the barrier layer was improved. The period has shortened considerably.

On the other hand, according to Example 3 in which the content ratio of the electrically conductive material was increased by containing 5 mass% of the AB having an average particle diameter of 55 nm without changing the content ratio of the AB having an average particle diameter of 35 nm, the barrier layer was maintained while maintaining a practically sufficient water resistance period. Electroconductivity could be improved significantly.

The film resistance of the barrier layer-formed current collector (Example 4) in which the barrier layer was prepared in the same manner as described above except that the mass ratio of AB and PVDF having an average particle diameter of 35 nm was 40:60 was 4.2 mΩ · cm 2, and the water resistance was 30. In less than a second, water resistance fell further compared with Example 2. The barrier layer was prepared in the same manner as above except that the mass ratio of AB (first conductive powder) having an average particle diameter of 35 nm, AB (second conductive powder) having an average particle diameter of 55 nm, and PVDF was 30:10:60. The film resistance of the barrier layer-formed current collector (Example 5) was 4.3 m? · Cm 2, and the water resistance was 45 seconds. That is, also in these examples 4 and 5, it was confirmed that the effect which suppresses the fall of water resistance accompanying an increase of an electrically conductive material content ratio is obtained by using together a 1st, 2nd electroconductive powder.

In addition, the viscosity of the composition (NV 9 mass%) which concerns on Example 1 which contains 30 parts of AB which have an average particle diameter of 35 nm as a electrically conductive material was 12200 mPa * s, The thing which concerns on the example 4 which increased the content of copper AB to 40 parts The viscosity of the composition (NV 9 mass%) was 14350 mPa · s, which was greatly increased as compared with the composition of Example 1. On the other hand, a composition in which 10 parts out of 40 parts of AB having an average particle diameter of 35 nm used in Example 4 was replaced with an AB having an average particle diameter of 76 nm (that is, AB: 30 nm: The composition of NV 9 mass% contained in the mass ratio of 70) was remarkably low viscosity compared with the composition concerning Example 4. Therefore, NV of the said composition was made higher, suppressing the viscosity of the composition for barrier layer forming below the equivalent to the composition concerning Example 1. Specifically, the amount of NMP was reduced while maintaining the mass ratio 30:10:60 of the first and second conductive powders and the polymer material to prepare a composition for forming a barrier layer of about 12% by mass of NV (Example 6). The viscosity of the composition concerning this example 6 was 10350 mPa * s. The composition was applied to a current collector under the same gravure coating conditions as in Example 1 and dried to obtain a barrier layer-forming current collector having a barrier layer having a thickness of about 2.5 μm on both surfaces of the current collector. In addition, in the above, all the viscosity of the composition for barrier layer formation was measured at 25 degreeC using the Brookfield viscometer.

About the barrier layer forming collector which concerns on Example 6, it carried out similarly to Examples 1-5, and performed water resistance test and film resistance measurement. Table 2 shows their results and the schematic configuration of the barrier layer according to each example. This table also shows the data of Example 1 and Example 4 together.

As shown in Table 2, in the composition for barrier layer forming which concerns on Example 6, by using the 1st conductive powder and the 2nd conductive powder which has an average particle diameter twice or more of the said 1st conductive powder as a electrically conductive material, 1st Even if NV was improved 1.5 times compared with Example 1 and Example 4 which used only electrically-conductive powder, it was still possible to set it as the composition of the viscosity which can be apply | coated favorably on the same gravure application conditions as the composition concerning Example 1. FIG. Thus, by apply | coating a composition of solid content on the application conditions similar to Example 1, according to Example 6, the thicker (high coating weight) barrier layer compared with Example 1 was formed. The barrier layer which concerns on this example 6 showed sufficient water resistance of 200 second or more in water-resistance period, and electroconductivity was also favorable.

<Example 7>

In this example, AB (first conductive powder) having an average particle diameter of 35 nm and AB (second conductive powder) having an average particle diameter of 4 µm were used as the conductive material. The said 1st, 2nd electroconductive powder and PVDF were mixed with NMP so that the mass ratio of these materials might be 30: 3: 67, and NV might be about 9 mass%, and the composition for barrier layer formation was prepared. The composition was dried by gravure coating on both sides of the current collector so as to have a coating amount of about 2 g / m 2 (solid content basis) per side, thereby forming a barrier layer having a thickness (average thickness) of about 2 μm on both sides of the current collector. That is, the average particle diameter of the 2nd electroconductive powder used by this example is larger than the average thickness of a barrier layer.

<Example 8 to Example 11>

The mass ratios of AB having an average particle diameter of 35 nm and AB and PVDF having an average particle diameter of 4 µm were 30: 6: 64 (Example 8), 30: 9: 61 (Example 9), 30:12:58 (Example 10), and 30, respectively. A barrier layer having a thickness (average thickness) of about 2 μm was formed on both surfaces of the current collector except for the point of setting it to: 15: 55 (Example 11).

About the barrier layer forming electrical power collector which concerns on each of Examples 7-11, it carried out similarly to the above, and performed water resistance test and film resistance measurement.

In addition, the sheet-shaped electrode (electrode sheet) was produced using the barrier layer forming electrical power collector which concerns on each of Examples 1 and 7-11. That is, the lithium nickelate powder (positive electrode active material), acetylene black (conductive material) having an average particle diameter of 48 nm, and CMC (polymer material) have a mass ratio of 87: 10: 3 and NV of about 45% by mass. It mixed with ion-exchange water so that it may become, and the aqueous active material composition was prepared. The active material layer was formed by apply | coating and drying the said active material composition to the sample (barrier layer formation collector) which concerns on each case from the said barrier layer. The coating amount (solid content basis) of the active material composition was adjusted to be about 12.8 g / m 2 combined on both sides. In the state where the active material composition was dried, the total thickness including the current collector and the electrode films (barrier layer and active material layer) formed on both surfaces thereof was about 80 μm. This was pressed so that the whole thickness might be 64 micrometers.

The sheet resistance of the electrode sheets according to Examples 1 and 7 to 11 thus obtained was measured as follows.

[Sheet Resistance Measurement]

Two electrode sheets according to each of Examples 1 and 7 to 11 were overlapped, and a pressure of 2500 N was applied, and sheet resistance [Ω · cm 2] was measured by a four-terminal four probe method according to JIS K7194 in this state.

The results of the above water resistance evaluation, film resistance measurement, sheet resistance measurement, and schematic configuration of the barrier layer according to each example are shown in Table 3 and FIG. 8.

As shown in Table 3 and Fig. 8, the first conductive powder and the second conductive powder having different average particle diameters as the conductive material were in a ratio of about 10: 1 to 3: 1 and the total content was about 33 to 40 mass%. According to Examples 7 to 9 used in combination, the film resistance and the sheet resistance could be reduced while ensuring good water resistance of 3.5 minutes or more in the water resistance period. In addition, Examples 13-16 (refer Table 6) mentioned later are examples which used AB with an average particle diameter of 70 nm instead of AB which is an average particle diameter of 4 micrometers as 2nd electroconductive powder, respectively at the same ratio as Examples 7-10. . As can be seen from the comparison between these Examples 7 to 10 and Examples 13 to 16, in Examples 7 to 10 using AB having a larger average particle diameter than the thickness of the barrier layer as the second conductive powder, the second conductive powder When the content ratios were the same, a barrier layer having a lower film resistance (higher conductivity) than Examples 13 to 16 could be formed. As shown in the schematic diagram shown in FIG. 7, since the particles of the second conductive powder 332 larger than the thickness of the barrier layer 33 protrude and the surface of the barrier layer 33 is irregular, the barrier layer 33 is formed. A large contact area between the active material layer 35 and / or the second conductive powder 332 penetrates through the thickness of the barrier layer 33, thereby interfering with the second conductive powder 332. It is believed that this is due to the fact that a good conductive path can be formed between the layer 35 and the current collector 32.

In addition, in Examples 10 and 11 in which the content ratio of the second conductive powder was more than 10 parts (more specifically, 12 parts or more), the water resistance of the barrier layer was lowered. Here, the reduction in sheet resistance is not particularly observed for the electrode sheet prepared by applying the aqueous active material composition to the barrier layer-forming current collector according to Examples 10 and 11, in the present experiment, after applying the active material composition, It is considered that the time until drying was short.

In addition, also in the composition for barrier layer forming which concerns on Examples 7-11, a part of quantity of the electrically conductive material contained in the said composition is the 2nd electrically conductive powder with a large average particle diameter, and the electrically conductive material which consists only of 1st electrically conductive powder is the same. It was confirmed that the viscosity of the said composition can be made low compared with the composition containing a quantity. Therefore, the composition for barrier layer forming which concerns on these Examples 7-11 also has high solidification (for example, about NV12% or more, typically NV12-20%, without impairing coating workability similarly to Example 6). I think it can be done). According to the composition for barrier layer formation of such a solid content, a barrier layer with better water resistance and conductivity can be formed.

<Example 8a to 8d>

In the barrier layer composition which concerns on Example 8, the influence which the operation (preparation conditions) at the time of preparing the composition for barrier layer formation has on film resistance was examined.

That is, in Example 8, the total amount of the second conductive powder and the total amount of PVDF used for the preparation are combined with the total amount of NMP, the stirrer (a three-axis planetary kneader available from the Flymix Co., Ltd., trade name "TK Hibisdis) Permix ”was used to disperse and disperse uniformly. Here, the total amount of the first conductive powder to be used (here, 100 g) was sequentially added at a rate of 15 g per one time (wherein the last one was 10 g) at 5 minute intervals to prepare a barrier layer-forming composition.

In preparation of the composition for barrier layer forming which concerns on Examples 8a-8d, the quantity of the 1st electrically conductive powder thrown in per one time was changed from Example 8. That is, the amount of the first conductive powder (that is, the input rate of the first conductive powder) to be injected at 5 minute intervals is 5 g (Example 8a), 10 g (Example 8b), 20g (Example 8c) and 25 g ( Example 8d). In other respects, the composition for forming a barrier layer according to Examples 8a to 8d was prepared in the same manner as for the preparation for the composition for forming a barrier layer according to Example 8. In addition, also in any of Example 8 and Examples 8a-8d, stirring speed was made into fixed conditions (7 m / sec of speed | rates), and the whole stirring time was also made the same.

Using the composition for barrier layer forming which concerns on Examples 8a-8d, the barrier layer forming electrical power collector was produced like Example 8, and their film resistance was measured. The obtained result is shown in Table 4 and FIG.

As shown in these diagrams, among the above examples, the barrier layer having the highest conductivity was obtained from the composition for barrier layer formation prepared from the same addition rate as in Example 8. Further, the amount of the first conductive powder to be added per one time is set in the range of 1/10 (example 8b) to 1/5 (example 8c) of the total amount of the first conductive powder to be used, so that the amount per dose is used. Compared with more cases or less cases, the barrier layer with better conductivity could be formed.

<Example 8e>

The volatile content of AB (first conductive powder) having an average particle diameter of 35 nm used in Example 8 is 1%, and the volatile content of AB (second conductive powder) having an average particle diameter of 4 µm is 0.7%. In this example, AB (first conductive powder) having an average particle diameter of 35 nm and volatile matter of 1.4% and an average particle diameter of 4 µm and a volatile matter of 1.2% (second conductive powder) instead of AB having a small content of volatile matter. ), A composition for forming a barrier layer having the same composition as in Example 8 (i.e., a solvent composition of NV 9% by mass containing 1st conductive powder: 2nd conductive powder: PVDF in a mass ratio of 30: 6: 64) Was prepared in the same manner. Using this composition, the barrier layer was formed like Example 8, and the active material layer was formed similarly to the above, and the electrode sheet which concerns on Example 8e was obtained.

The lithium ion battery was produced using the electrode sheet which concerns on Example 8 and Example 8e as a positive electrode.

As the negative electrode, the followings were used. That is, natural graphite (powder), SBR, and CMC are mixed with ion-exchanged water such that the mass ratio of these materials is 98: 1: 1 and NV is 45% by mass to prepare an aqueous active material composition (negative electrode active material composition). It was. The composition was applied to both sides of a long copper foil (negative electrode current collector) having a thickness of about 15 μm, and dried to form a negative electrode active material layer. In the state where the negative electrode active material composition was dried, the thickness of the whole including the current collector and the negative electrode active material layers formed on both surfaces thereof was about 120 μm. This was pressed so that the whole thickness might be 85 micrometers. In this manner, a sheet-shaped negative electrode (negative electrode sheet) was produced.

The negative electrode sheet and the electrode sheet (positive electrode sheet) according to each example were laminated together with two long separators (here, a porous polyethylene sheet was used), and the laminated sheet was wound in the long direction to produce a wound electrode body. It was. This electrode body was accommodated together with the nonaqueous electrolyte in a laminate film container to construct a lithium ion battery having a capacity of about 500 kW. As the nonaqueous electrolyte, an electrolytic solution having a composition in which a supporting salt (herein, LiPF ₆ ) was dissolved in a 3: 7 (volume ratio) mixed solvent of EC and DEC at a concentration of 1 mol / L was used.

Conditioning treatment suitable for the lithium ion battery constructed as described above (for example, constant current charge for 3 hours at a charge rate of 1/10 C, followed by charging at constant current constant voltage to 4.1 V at a charge rate of 1/3 C, and 1 After the initial charge / discharge treatment of repeating the operation of constant current discharge to 3.0V at a discharge rate of / 3C two to three times) was performed, the amount of gas generation was measured by an aqueous phase replacement method. The result is shown in Table 5 with the volatile matter of the electrically conductive material used for each example.

As shown in Table 5, the amount of gas generated in the battery according to Example 8 using AB having 1% or less of volatile matter in either of the first and second conductive powders was 1.5 mL, whereas in Example 8e using more volatile AB. The gas generation amount of the battery was 3.3 mL. From the above, it was confirmed that an effect of further reducing the amount of generated gas can be obtained by forming a barrier layer using a carbon material having a less volatile content (preferably 1% or less volatile content) as the conductive material.

<Example 12>

AB and PVDF with an average particle diameter of 40 nm were mixed with NMP so that the mass ratio of these materials became 30:70 and NV became about 9 mass%, to prepare a composition for forming a barrier layer. Using this composition, a barrier layer having a thickness of about 2 μm was formed on both surfaces of the current collector in the same manner as in Example 1.

<Example 13>

In this example, AB (first conductive powder) having an average particle diameter of 40 nm and AB (second conductive powder) having an average particle diameter of 70 nm were used as the conductive material. The said 1st, 2nd electroconductive powder and PVDF were mixed with NMP so that the mass ratio of these materials might be 30: 3: 67, and NV might be about 9 mass%, and the composition for barrier layer formation was prepared. Using this composition, a barrier layer having a thickness of about 2 μm was formed on both surfaces of the current collector in the same manner as in Example 1.

<Examples 14 to 16>

The mass ratio of AB having an average particle diameter of 40 nm and AB having an average particle diameter of 70 nm and PVDF is 30: 6: 64 (Example 14), 30: 9: 61 (Example 15), and 30:12:58 (Example 16). A barrier layer having a thickness of about 2 μm was formed on both surfaces of the current collector except in the same manner as in Example 13.

The water resistance and the film resistance of the barrier layer forming current collector produced in Examples 12 to 16 were measured in the same manner as above. The results are shown in Table 6 together with the schematic configuration of the samples relating to each example and the data of example 1.

In addition, after maintaining the barrier layer forming collectors prepared in Examples 1 and 12 to 16 in a room having a temperature of 20 ° C. and a relative humidity of 65% for 3 days, the amount of moisture (adsorbed moisture content) contained in each barrier layer forming collector. Was measured by a general curl fisher method. The obtained result is combined with Table 6 and shown.

In addition, the specific surface area of AB having an average particle diameter of 35 nm used above was 68 m 2 / g, the specific surface area of AB having an average particle diameter of 40 nm was 58 m 2 / g, and the specific surface area of AB having an average particle diameter of 70 nm was 27 m 2 / g. to be. From the values of these specific surface areas and the composition and thickness of each barrier layer (here both 2 μm), the specific surface area of the conductive material contained per unit area (one cm per side) of the barrier layer according to each example (ie, 1 cm × 1). The total surface area of the conductive material contained in the barrier layer of cm × 2 μm, hereinafter referred to as “containing surface area”) was calculated. The result is combined with Table 6 and shown.

As shown in Table 6, in the barrier layer according to Example 1 and Example 12, in which only one type of AB was used at the same content ratio, the content surface area was reduced by using AB having a larger average particle diameter (smaller specific surface area). . When this containing surface area becomes small, the amount of adsorption moisture of the barrier layer decreases. This decrease in the amount of adsorption water is such that when the electrode body having the electrode sheet having the barrier layer is housed together with the nonaqueous electrolyte in a housing to construct a battery (for example, a lithium ion battery), the amount of moisture introduced into the housing is measured. It can help to reduce it. Reducing the water intake into the housing is preferable because it has the effect of reducing the amount of gas generated when conditioning is performed by a conventional method, for example, after battery construction. However, in Example 12 in which AB having an average particle diameter of 35 nm was simply replaced with AB having an average particle diameter of 40 nm, the effect of improving the conductivity of the barrier layer in comparison with Example 1 was not obtained.

On the other hand, according to Examples 13 to 16 using the first conductive powder and the second conductive powder having a larger average particle diameter than the powder, the increase in the containing surface area accompanied by the increase in the content ratio of the conductive material (and further, the increase in the amount of adsorption moisture) ), The conductivity of the barrier layer could be improved. Among them, Examples 13 to 15 in which the first conductive powder and the second conductive powder having different average particle diameters were used together as a conductive material in a ratio of about 10: 1 to 3: 1 and the total content was about 33 to 40 mass%. (The said surface area is 40 cm <2> / cm <2> -2 micrometer or less, More specifically, it exists in the range of 35-40 cm <2> / cm <2> micrometer), It is possible to improve conductivity while ensuring good water resistance and to suppress the amount of adsorption moisture. Could.

As mentioned above, although this invention was demonstrated in detail, the said embodiment is only an illustration, The invention disclosed here includes what changed and modified various specific examples mentioned above.

Since the lithium ion battery which concerns on this invention has the outstanding performance (output performance etc.) as mentioned above, it can be used suitably as a power supply for motors (motors) mounted in vehicles, such as an automobile, for example. Such lithium ion batteries may be used in the form of assembled batteries in which a plurality of them are connected in series and / or in parallel. Accordingly, the present invention, as schematically shown in FIG. 6, includes a vehicle (typically an automobile, in particular a hybrid vehicle, an electric vehicle) having such a lithium ion battery (which may be in the form of an assembled battery) 10 as a power source. And a motor vehicle having an electric motor such as a fuel cell vehicle.

Claims (9)

An active material layer containing the electrode active material as a main component is an electrode held in a metal current collector,
On the surface of the current collector, a barrier layer containing a conductive material and a water-insoluble polymer material is formed,
Here, the said conductive material contains the 1st conductive powder of a predetermined average particle diameter, and the 2nd conductive powder which is larger in average particle diameter than the said 1st conductive powder, and the content rate of the said 1st conductive powder in the said barrier layer is An electrode more than the content rate of the said 2nd conductive powder. The electrode of Claim 1 whose average particle diameter of a said 2nd conductive powder is 2 times or more of the average particle diameter of the said 1st conductive powder. The electrode of Claim 1 whose average particle diameter of a said 2nd electroconductive powder is larger than the thickness of the said barrier layer. It is a method of manufacturing the electrode hold | maintained in the metal electrical power collector whose active material layer which uses an electrode active material as a main component,
Preparing a barrier layer-forming composition comprising a conductive material, a water-insoluble polymer material and a solvent in which the polymer material is dissolved;
Providing the barrier layer-forming composition to the current collector to form a barrier layer on the surface of the current collector;
It includes forming an active material layer by applying an aqueous active material composition to the current collector on which the barrier layer is formed,
Here, the said barrier layer forming composition uses the 1st electroconductive powder of a predetermined average particle diameter, and the 2nd electroconductive powder whose average particle diameter is larger than a said 1st electroconductive powder as said electroconductive material, and the said 1st electroconductive powder of The electrode manufacturing method prepared so that content rate may become more than content rate of the said 2nd conductive powder. The electrode manufacturing method according to claim 4, wherein the barrier layer-forming composition is prepared by mixing the second conductive powder and the non-aqueous polymer material with the solvent, and then mixing the first conductive powder with the mixture. . The electrode manufacturing method of Claim 5 whose solvent which comprises the said composition for barrier layer formation is an organic solvent. A battery constructed using the electrode according to claim 1. The lithium ion battery built using the electrode of Claim 1 as a positive electrode. A vehicle comprising the lithium ion battery according to claim 8.

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